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/*
Copyright (C) 2012-2021 Carl Hetherington <cth@carlh.net>
This file is part of DCP-o-matic.
DCP-o-matic is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
DCP-o-matic is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with DCP-o-matic. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef DCPOMATIC_SIGNAL_MANAGER_H
#define DCPOMATIC_SIGNAL_MANAGER_H
#include "exception_store.h"
#include "io_context.h"
#include <boost/asio.hpp>
#include <boost/thread.hpp>
class Signaller;
/** A class to allow signals to be emitted from non-UI threads and handled
* by a UI thread.
*/
class SignalManager : public ExceptionStore
{
public:
/** Create a SignalManager. Must be called from the UI thread */
SignalManager ()
: _work(dcpomatic::make_work_guard(_context))
{
_ui_thread = boost::this_thread::get_id ();
}
virtual ~SignalManager () {}
SignalManager (Signaller const&) = delete;
SignalManager& operator= (Signaller const&) = delete;
/* Do something next time the UI is idle */
template <typename T>
void when_idle (T f) {
dcpomatic::post(_context, f);
}
/** Call this in the UI when it is idle.
* @return Number of idle handlers that were executed.
*/
size_t ui_idle () {
/* This executes one of the functors that has been post()ed to _context */
return _context.poll_one();
}
/** This should wake the UI and make it call ui_idle() */
virtual void wake_ui () {
/* This is only a sensible implementation when there is no GUI */
ui_idle ();
}
private:
/** Emit a signal from any thread whose handlers will be called in the UI
* thread. Use something like:
*
* ui_signaller->emit (boost::bind (boost::ref (SomeSignal), parameter));
*/
template <typename T>
void emit (T f) {
if (boost::this_thread::get_id() == _ui_thread) {
/* already in the UI thread */
try {
f ();
} catch (...) {
store_current ();
}
} else {
/* non-UI thread; post to the context and wake up the UI */
dcpomatic::post(_context, f);
wake_ui ();
}
}
friend class Signaller;
/** A io_context which is used as the conduit for messages */
dcpomatic::io_context _context;
/** Object required to keep io_context from stopping when it has nothing to do */
dcpomatic::work_guard _work;
/** The UI thread's ID */
boost::thread::id _ui_thread;
};
extern SignalManager* signal_manager;
#endif
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